Some options at the $10 price point on AliExpress, though I cannot recommend one, maybe another reader can. CTs are the generally accepted way to do this and don't have to modify mains wiring. Could also build your own; CTs are inexpensive.

A bit funny, but I personally found "please learn to never..." to be MUCH more off-putting and patronizing than the "why not just...".

Maybe just something about the latter being interpreted as a question, and the former being interpreted as an order.

Thanks Dad.